The evidence statements provide detail on what students should know and be able to do in order to satisfy each performance expectation (PE) at the end of instruction. Given that each PE is three-dimensional, the statements describe how students can use the practices, crosscutting concepts, and disciplinary core ideas together to demonstrate proficiency on the PEs by the end of instruction.
They are intended to identify clear, measurable components that, if met, fully satisfy each PE described within the NGSS. They are not meant to limit or dictate instruction and were written to allow for multiple methods and contexts of assessment, including assessing multiple related PEs together at the same time.
The evidence statements were developed by educators and scientists, including many members of the NGSS writing team. For more information, see the overview.